Cellulose organic ester compositions containing tri-ethylene glycol di-alpha-hydroxyisobutyrate



Patented Sept. 8, 1936 UNITED STATES PATENT OFFICE RATE Henry B. Smith,Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., acorporation of New York No Drawing. Application November 13, 1935,Serial No. 49,540

7 Claims.

This invention relates to compositions of matter in which celluloseorganic acid esters, such as cellulose acetate, are combined or mixedwith other substances, such as a compatible plasticizer, with or withouta common solvent for both, and with or without other useful additionagents, so that the resulting product will have properties such as willmake the composition highly advantageous for use in the plastic andanalogous arts, such, for instance, as the manufacture of wrappingsheets or tissue, photographic film, mlding compounds and products,artificial silk, varnishes or lacquers, coating compositions and thelike.

One object of this invention is to produce com positions of matter whichmay be made into permanently transparent, strong and flexible sheets orfilms of desired thinness which are substantially waterproof, areunaffected by ordinary photographic fluids and possess the desiredproperties of a. support for sensitive photographic coatings. Anotherobject of my invention is to produce compositions of matter which arecapable of easy and convenient manipulation in the plastic and analogousarts, such as in the manufacture of sheets, film, artificial silkfilaments, varnishes, lacquers and the like, and to produce compositionswhich will not injure, or be injured by, the substances or surfaces withwhich they are associated during manufacture. Another object of myinvention is to produce compositions which can be molded at elevatedtemperatures and high pressures to produce plastic products having thedesirable properties of celluloid. Other objects will become apparent tothose skilled in the art to which this invention pertains.

While cellulose acetate has been known for decades, it has also beenknown that to utilize it in the various plastic arts it is necessary tomix therewith various plasticizing or conditioning agents. Certain ofthese and other addition agents are also added for the purpose ofreducing the inflammability of the: product. Plastic inducing agents,such as the higher alcohols. and their esters, are sometimes also added.Similarly, addition compounds of various kinds have been employed toincrease flexibility, transparency, toughness and other properties whichwill enhance the value of the resulting product. Addition products forthe same or similar purposes are also added to cellulose acetate toprepare it for use in the other plastic arts, such as in the manufactureof lacquers, varnishes, arti-. ficial silk filaments, molded compoundsand the like. While the plasticizers or other addition agents heretoforediscovered have had their utility in the art, the increasing use towhich cellulose acetate has been put and the increasing number ofdesirable properties required of cellulose acetate for most purposeshave made the discovery of new and economical plasticizers or otheraddition agents a matter of considerable importance to the art. This hasbeen a problem of some difficulty, since many of the nitrocellulosesolvents are not solvents for cellulose acetate, and many substanceswhich act as plasticizers for nitrocellulose are not compatible or atleast not sufiiciently compatible with cellulose acetate to be used asplasticizers in cellulose acetate compositions.

I have discovered that valuable properties may be induced in and/orcontributed to compositions containing organic acid esters of cellulose,such as cellulose acetate, by adding thereto, as a plasticizingcompound, triethylene glycol dialpha-hydroxy isobutyrate. Theparticularly useful properties which this compound induces in orcontributes to cellulosic compositions containing it are hereinafterenumerated.

Triethylene glycol di-alpha-hydroxy isobutyrate has the structuralformula and may be prepared as follows:

416 grams (4 gram-moles) of alpha-hydroxy isobutyrlc acid, 300 grams (2gram-moles) of triethylene glycol, 10 grams of p-toluene sulfonic acid(as a catalyst), and kilograms of dry toluene are mixed together in awide-mouth 12- liter flask and heated on a steam bath, under a refluxcondenser, until all the solid has dis solved. Due to the formation ofan oil layer on the bottom of the reaction mixture, mechanical stirringis necessary before heating over a free flame. At this point, therefore,the flask is provided with a mechanical stirrer, as well as with a 3-ft.fractionating column. The reaction mixture is then distilled slowly overa free flame, with mechanical stirring. When about 500 cc. of distillatehas been collected, the receiver is changed. The Water layer in thebottom of the receiver is separated, and its volume recorded. The upperlayer (toluene) is returned to the reaction mixture. This process iscontinued until 34 cc. of water has'been collected, which requires about20 hours. At this point the reaction mixture contains a small amount ofsolid material, possibly p-toluenesulfonate, and this is filtered out bygravity.

The filtrate, now free from layers, is further distilled withoutmechanical stirring, using a small iii-bubbler fractionating column ofthe Clarke and Rahrs type, which is more fully de.-. scribedhereinafter. Because of the slow formation of water from this point on,the flame is ad.-. justed so as to raise the vapors just to the tenthbubbler. After the liqui has, be boiled in fashion for a few hours, asmall amount of Water collects in the upper bubblers. At these intervalsthe flame is increased sufflciently just to distil over what moisturehas collected in the upper bubblers. When these bubblers are againclear, the flame is decreased and refluxing is continued as alreadydescribed. This procedure is continued until no more water can beremoved. A total of 60 cc. (theory '72 cc.) is removed, which takesabout 50 hours. The residue, when cold, is filtered by gravity,neutralized with a weak S0111: tion of potassium carbonate, and washedonce with water.. The washed material is distilled under slightlyreduced pressure over a steam bath to remove the toluene. The residue isfurther distilled under reduced pressure over a free flame, a smallantifoam distillation flask with a water: cooled side-arm receiver,which is more fully described hereinafter, being used. Cuts are taken asfollows: upto 150 C./l mm., 150: 178 C./1 mm., 178-180 C./1 mm., andresidue. The fraction coming over at 178=180 C./1 mm. is triethyleneglycol diealphaehydroxy isobutyrate. It is light yellow in color, andbecomes cloudy almost immediately after distillation. Due to the natureof the reaction, each batch should be identified by analysisin order tomake certain that it is triethylene glycol di-alphaehydroxy isobutyrate.v

The bubbler fractionating cohunn of the Clarke and Rahrs type isdescribed in Industrial .8: En:

gineer-ing Chemistry 18, 1092 (19.26). An im: improvement therein isdescribed infSynthetic Grganic Chemicals, published by the Eastman KodakCo., vol. IV, No. 5, July, 1931, as follows:

The operation of the Clarke-Rahrs type of bubbler column can be improvedby a slight change in the liquid return tube. If the narrow er w one ioo n d otho unit below t a small upward bend in the form of a J, a trapis formed which prevents any of the vapor escaping through the tubeinstead of bubbling through the liquid. The change overcomes thedifilculty that was sometimes encountered when the dis-.-

1 tillation was pushed too rapidly. In this slightly modified form thereis no chance for the vapor to proceed upward in the column withou itfirst being washed by the liquid condensate collected in the bottom ofeach unit.

The anti-foam distillation flask with watercooled side-arm receiver isdescribed in Syn thetic Organic Chemicals, vol. IV, No. 2 Dee cember,1930, as follows:

The distilling flask is made from a three-liter, long-neck, pyrex flask,which is connected by means of a 28 mm. tube to a two-liter, long-neckflask. A trap is sea ed in h bo tom oi the smaller flask and connect dwit e return tube to the distilling vessel. The remainder of the set-uis the usu l conden i roooiverottao ioe o the vacuum p mp via. he s fetyron and. m nometer.

Di tillation is tar ed as su l an h n the roth re ohes the ese voirflask he ubbles pond and eak The liquid o lleote n the troll below andis returned to the boiling flask. It is sometimes necessary, at thebeginning, to warm the second flask with a small flame, but as soon asthe distillation gets under way, the additional heating can bediscontinued. I ittle attention to the apparatus is necessarythereafter.

In order that those skilled in this art may better understand myinvention I would state, by way of illustration, that for themanufacture oij photographic film base or other sheets my newcompositions of matter may be compounded as follows: 100 parts ofacetone-soluble cellulose acetate i. e., cellulose acetate containingfrom about 36% to 42% acetyl radical, approximately, is dissolved withstirring at atmospheric temperature in 300 to'500 parts, preferably 400parts, by weight, Q! acetone, To this solution may be added from 5 to 50parts by weight of triethylene glycol di-alpha-hydroxy isobutyrate.Within the limits stated, the amount of plasticizer may be decreased orincrease p ndin up Wh h r it is desired to deoreosoor ncrease, respe tivly, th propertie which this pl st izor contribu es to the. finished prou t... The mount i s lvent employed may also b increas d or decr ased,depend n upon whethe it is des e to ha e a. m re or l s free y flowincomposition, espeo tively,

A ompo ition of matt pr pared as a ove des ri ed may be depos d u on anysu table filinforming su faoo and th acet ne evapo ated. the from toform a film or sheet, in a man er well known to those s illed i the ar Afilo; so produced has permanently brilliant trans-v parenoyand l winflominabil ty. urning. no mo readi y than or inar news int, F m orshoots produced in aooo da cowlth m ovontionoro very tou h anflexible... F r ns ance fi ms o o llulose ac tate plast o zod with fro29% to 30%. f triethy en col oilolio-h droxy i. .obutyrate. (2on1 aop rtby weight nor .0 nor-ts by wei ht of cellu ose ac tate) had. n iolflexibility from 2.35% to 265% reater t an of film containin no plastiizor Fur he more, film so plastioized m intains flexibil a elk- Deriorfashion. For in tance at 0-, conta n n from. 20% to 3.0% f trieth l ne lcol diealpha-nydr x s butyroto ma ntained flexibility for 170 days, wheras. nn rlostio od film became brittle in 3.0. d ys.-

in ates that. films. or sheets s n sti izod. will ith tend ordinaryusage satisfactoril for m n yea s:

Qther similar so ve ts (i stea oi acetone). which are compatible withthe. cellulo e a tate and my new plastioi er will also o ur totli ooskilled in this art. such as et ylene h ori ealcohol mixtures. In likemanner this piasticizer may be compounded with ot er sin l or an acidesters of cellulose, such as cel ulose BIO- pionate, hutyrate, stearateand. the l ke. r w th mixed Qrganicacid esters, suc a cell oseoootostearate, cellulose. aeeto pro iooote: ellulose acetorbutyrato,cellulose. aooto-l otate. cellulose aceto-tartrate or the like asuitable s vent wh ch will d ssolve. both the ool olosi erivative nd theplastici r bein employ d oon. for i istance, as an alkylene chloride witQ 2 with ut the od itionoi a ohol- In smiio as. m aoo o-oo o ibod oo nosti o matte use ul he. pr du io o l v nd hoots. t w ll b a pa nt ha y newploe oi oi? may als be emp o ed w d an in the other branches of theplastic art, For insta c my no el nloo z r m e m y d in connection witha number of the known lace quer and varnish formulae with which it maybe found to be compatible. In such cases the plasticizer is usuallyfirst put into solution in' the cellulose derivative solution, and ifnon-solvents are added for the purpose of cheapening the compositionthey are added only to such an extent as will not precipitate thederivative from solution. Other uses within the scope of my inventionwill also suggest themselves to those skilled in the art and are to beincluded within the scope of the claims appended hereto.

Triethylene glycol di-alpha-hydroxy isobutyrate may also beadvantageously used as a plasticizer in cellulose organic acid estermolding compositions. For instance, when about 30% (30 parts by weightper 100 parts of cellulose acetate) of triethylene glycoldi-alpha-hydroxy isobutyrate is homogeneously mixed with celluloseacetate, the mixture may be converted into a hard, transparent ortranslucent plastic product by molding at a temperature of 140-160" C.and a pressure of 2500 to 4000 pounds per square inch for a period offrom 2 to 5 minutes, in a manner already known to those skilled in molding compounds of that nature.

While we have referred particularly to triethylene glycoldi-alpha-hydroxy isobutyrate, it will be apparent that we may also usethe diesters of triethylene glycol with other hydroxy butyric acids.These esters can be prepared in the manner described for the preparationof triethylene glycol di-alpha-hydroxy isobutyrate,

another hydroxy butyric acid being used in place of alpha-hydroxyisobutyric acid.

What I claim as my invention and desire to be secured by Letters Patentof the United States 1. A composition of matter comprising a celluloseorganic acid ester and triethylene glycol di-alpha-hydroxy isobutyrate.

2. A composition of matter comprising cellulose acetate and triethyleneglycol di-alpha-hydroxy isobutyrate.

3. A transparent, flexible sheet comprising 100 parts of a celluloseorganic acid ester and, as a plasticizer therefor, about 5 to parts, byweight, of triethylene glycol di-alpha-hydroxy isobutyrate.

4. A transparent, flexible sheet comprising parts of cellulose acetateand, as a plasticizer therefor, about 5 to 50 parts, by weight, oftriethylene glycol di-alpha hydroxy isobutyrate.

5. A molding composition adapted for molding under elevated temperaturesand high pressures, comprising a cellulose organic acid ester andtriethylene glycol di-alpha-hydroxy isobutyrate.

6. A molding composition adapted for molding under elevated temperaturesand high pressures, comprising cellulose acetate and triethylene glycoldi-alpha-hydroxy isobutyrate.

'7. A composition of matter comprising a cellulose organic acid esterand a triethylene glycol bis-hydroxybutyrate.

HENRY B. SMITH.

